The present invention relates to an air-float fixture support system for machine tool and other environments, and in particular to a power translation apparatus wherein the workpiece fixture may be automatically moved from one position to another on the air-float table.
In the past, the machining of large workpieces involved very difficult poisitioning and repositioning of the workpiece when the various portions thereof are machined. In many cases, it is necessary to use hoists for elevating and moving the workpiece about both to and from the machine tool table, and on the table itself where repositioning is necessary for sequential machining steps.
In order to overcome these problems, an air-float system, wherein the workpiece is mounted to a fixture which in turn is supported on a film of pressurized air, has been developed. This system is described in detail in U.S. Pat. No. 4,058,885 in the name of Raymond A. Bergman, which patent is incorporated herein by reference. In the system, a table is provided with fluid passages and a plurality of fluid outlets distributed over the surface of the table so that a cushion of pressurized air may be provided underneath the workpiece fixture. By virtue of the fluid pressure film, substantially friction-free movement of the fixture on the table is possible thereby permitting positioning and repositioning to be accomplished by a single operator without the need for hoisting equipment.
In order for the fixture to be rotated and translated from one position to another, the table is provided with one or more retractable pivot pins which project upwardly from the table surface. The pins may either be receivable in a socket in the bottom of the fixture, in which case the fixture is constrained to move circularly on the table, or, alternatively, they may be received in one or more slots so that the fixture is not only rotatable but also translatable. Cooperating pairs of retractable pin and socket locating devices on the fixture and table provide for accurate location of the fixture in a variety of predetermined positions. Clamps may also be provided for clamping the fixture in the located positions during machining. The clamps may either be of the conventional T-slot type, or, alternatively, of the bayonet type as described in pending U.S. Patent application No. 829,358 filed Aug. 31, 1977 in the name of Raymond A. Bergman.
The table may be provided with a dual centering pin feature if additional flexibility is desired in positioning and locating the fixture. The dual centering pin comprises an outer pin which is engageable with the fixture slots, and an inner pin received within the outer pin with means for causing the inner pin to extend upwardly out of the outer pin so as to engage holes in the slots. When the inner pin is retracted, the workpiece fixture is translatable on the table in engagement with the outer pin, and when the inner pin is extended and received within one of the fixture holes within the slots, the fixture may be rotated about it to the desired position.
With the advent of numerical control machine tools, there have been many advances in automating lathes, milling machines, presses and the like to the point where parts, and even tools, can be loaded and unloaded without the necessity for direct operator handling. Because of the complexity of the operations necessary for accomplishing the automated loading and unloading, however, these developments have been limited to relatively small parts and tools.
A need still remains for the automatic transport, loading and unloading of large workpieces for automatic machining wherein large parts would be translated through a machine shop and moved into and out of various machining stations under total automatic control. The heart of such a system is the ability to capture the workpiece supporting fixture plate or pallet as it reaches the appropriate machining station on a conventional conveyor system, and move it from the conveyor to the work station. The workpiece and fixture would then be moved into a positive, accurate location in the working area in order to enable accurate machining. Once in this position, conventional numerical controlled prior art machines would perform the necessary machining operations until repositioning of the workpiece is required.
Although the prior developments of the air-float system as described above have greatly facilitated the positioning and repositioning of workpieces within the tool station, manual repositioning by the operator was necessary. Furthermore, large traveling hoists are necessary for transporting the workpiece to the machine tool station, and then removing it after all the machining steps have been accomplished. This results in substantial machine down time because the operator must wait for the hoist to become available to remove the machined part, and then wait again for the hoist to become available to deliver the next part for machining. Another drawback is the inherent danger in lifting and transporting extremely heavy workpieces above the working area.